diff --git a/oneko.js b/oneko.js
new file mode 100644
index 0000000..7ba7c74
--- /dev/null
+++ b/oneko.js
@@ -0,0 +1,239 @@
+// oneko.js: https://github.com/adryd325/oneko.js
+
+(function oneko() {
+  const isReducedMotion =
+    window.matchMedia(`(prefers-reduced-motion: reduce)`) === true ||
+    window.matchMedia(`(prefers-reduced-motion: reduce)`).matches === true;
+
+  if (isReducedMotion) return;
+
+  const nekoEl = document.createElement("div");
+
+  let nekoPosX = 32;
+  let nekoPosY = 32;
+
+  let mousePosX = 0;
+  let mousePosY = 0;
+
+  let frameCount = 0;
+  let idleTime = 0;
+  let idleAnimation = null;
+  let idleAnimationFrame = 0;
+
+  const nekoSpeed = 10;
+  const spriteSets = {
+    idle: [[-3, -3]],
+    alert: [[-7, -3]],
+    scratchSelf: [
+      [-5, 0],
+      [-6, 0],
+      [-7, 0],
+    ],
+    scratchWallN: [
+      [0, 0],
+      [0, -1],
+    ],
+    scratchWallS: [
+      [-7, -1],
+      [-6, -2],
+    ],
+    scratchWallE: [
+      [-2, -2],
+      [-2, -3],
+    ],
+    scratchWallW: [
+      [-4, 0],
+      [-4, -1],
+    ],
+    tired: [[-3, -2]],
+    sleeping: [
+      [-2, 0],
+      [-2, -1],
+    ],
+    N: [
+      [-1, -2],
+      [-1, -3],
+    ],
+    NE: [
+      [0, -2],
+      [0, -3],
+    ],
+    E: [
+      [-3, 0],
+      [-3, -1],
+    ],
+    SE: [
+      [-5, -1],
+      [-5, -2],
+    ],
+    S: [
+      [-6, -3],
+      [-7, -2],
+    ],
+    SW: [
+      [-5, -3],
+      [-6, -1],
+    ],
+    W: [
+      [-4, -2],
+      [-4, -3],
+    ],
+    NW: [
+      [-1, 0],
+      [-1, -1],
+    ],
+  };
+
+  function init() {
+    nekoEl.id = "oneko";
+    nekoEl.ariaHidden = true;
+    nekoEl.style.width = "32px";
+    nekoEl.style.height = "32px";
+    nekoEl.style.position = "fixed";
+    nekoEl.style.pointerEvents = "none";
+    nekoEl.style.imageRendering = "pixelated";
+    nekoEl.style.left = `${nekoPosX - 16}px`;
+    nekoEl.style.top = `${nekoPosY - 16}px`;
+    nekoEl.style.zIndex = Number.MAX_VALUE;
+
+    let nekoFile = "./oneko.gif"
+    const curScript = document.currentScript
+    if (curScript && curScript.dataset.cat) {
+      nekoFile = curScript.dataset.cat
+    }
+    nekoEl.style.backgroundImage = `url(${nekoFile})`;
+
+    document.body.appendChild(nekoEl);
+
+    document.addEventListener("mousemove", function (event) {
+      mousePosX = event.clientX;
+      mousePosY = event.clientY;
+    });
+
+    window.requestAnimationFrame(onAnimationFrame);
+  }
+
+  let lastFrameTimestamp;
+
+  function onAnimationFrame(timestamp) {
+    // Stops execution if the neko element is removed from DOM
+    if (!nekoEl.isConnected) {
+      return;
+    }
+    if (!lastFrameTimestamp) {
+      lastFrameTimestamp = timestamp;
+    }
+    if (timestamp - lastFrameTimestamp > 100) {
+      lastFrameTimestamp = timestamp
+      frame()
+    }
+    window.requestAnimationFrame(onAnimationFrame);
+  }
+
+  function setSprite(name, frame) {
+    const sprite = spriteSets[name][frame % spriteSets[name].length];
+    nekoEl.style.backgroundPosition = `${sprite[0] * 32}px ${sprite[1] * 32}px`;
+  }
+
+  function resetIdleAnimation() {
+    idleAnimation = null;
+    idleAnimationFrame = 0;
+  }
+
+  function idle() {
+    idleTime += 1;
+
+    // every ~ 20 seconds
+    if (
+      idleTime > 10 &&
+      Math.floor(Math.random() * 200) == 0 &&
+      idleAnimation == null
+    ) {
+      let avalibleIdleAnimations = ["sleeping", "scratchSelf"];
+      if (nekoPosX < 32) {
+        avalibleIdleAnimations.push("scratchWallW");
+      }
+      if (nekoPosY < 32) {
+        avalibleIdleAnimations.push("scratchWallN");
+      }
+      if (nekoPosX > window.innerWidth - 32) {
+        avalibleIdleAnimations.push("scratchWallE");
+      }
+      if (nekoPosY > window.innerHeight - 32) {
+        avalibleIdleAnimations.push("scratchWallS");
+      }
+      idleAnimation =
+        avalibleIdleAnimations[
+          Math.floor(Math.random() * avalibleIdleAnimations.length)
+        ];
+    }
+
+    switch (idleAnimation) {
+      case "sleeping":
+        if (idleAnimationFrame < 8) {
+          setSprite("tired", 0);
+          break;
+        }
+        setSprite("sleeping", Math.floor(idleAnimationFrame / 4));
+        if (idleAnimationFrame > 192) {
+          resetIdleAnimation();
+        }
+        break;
+      case "scratchWallN":
+      case "scratchWallS":
+      case "scratchWallE":
+      case "scratchWallW":
+      case "scratchSelf":
+        setSprite(idleAnimation, idleAnimationFrame);
+        if (idleAnimationFrame > 9) {
+          resetIdleAnimation();
+        }
+        break;
+      default:
+        setSprite("idle", 0);
+        return;
+    }
+    idleAnimationFrame += 1;
+  }
+
+  function frame() {
+    frameCount += 1;
+    const diffX = nekoPosX - mousePosX;
+    const diffY = nekoPosY - mousePosY;
+    const distance = Math.sqrt(diffX ** 2 + diffY ** 2);
+
+    if (distance < nekoSpeed || distance < 48) {
+      idle();
+      return;
+    }
+
+    idleAnimation = null;
+    idleAnimationFrame = 0;
+
+    if (idleTime > 1) {
+      setSprite("alert", 0);
+      // count down after being alerted before moving
+      idleTime = Math.min(idleTime, 7);
+      idleTime -= 1;
+      return;
+    }
+
+    let direction;
+    direction = diffY / distance > 0.5 ? "N" : "";
+    direction += diffY / distance < -0.5 ? "S" : "";
+    direction += diffX / distance > 0.5 ? "W" : "";
+    direction += diffX / distance < -0.5 ? "E" : "";
+    setSprite(direction, frameCount);
+
+    nekoPosX -= (diffX / distance) * nekoSpeed;
+    nekoPosY -= (diffY / distance) * nekoSpeed;
+
+    nekoPosX = Math.min(Math.max(16, nekoPosX), window.innerWidth - 16);
+    nekoPosY = Math.min(Math.max(16, nekoPosY), window.innerHeight - 16);
+
+    nekoEl.style.left = `${nekoPosX - 16}px`;
+    nekoEl.style.top = `${nekoPosY - 16}px`;
+  }
+
+  init();
+})();
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